Device for ambient thermal and vibration energy harvesting

ABSTRACT

An integrated circuit on a chip may include a plurality of capacitors that are connected in series and generate an AC noise signal. A selected bandwidth of the AC noise signal transmits through the series of capacitors as a first AC power signal. Respective rectifiers are positioned for receiving a positive cycle of the first AC power signal and a negative cycle of the first AC power signal. Output terminals are connected to the respective rectifiers and configured for connection to an off chip circuit. The capacitors may be fixed or variable gap capacitors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to and incorporates by reference U.S.Provisional Patent Application Ser. No. 63/013,631 filed on Apr. 22,2020, and entitled Ambient Thermal and Vibration Energy Harvesting.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH

The research presented in this disclosure has not relied on anygovernment funds during development operations.

FIELD

The disclosed technology generally relates to systems, devices, andmethods for harvesting thermal and vibrational energy.

BACKGROUND

Energy harvesting is the practice of capturing traditional power fromexternal sources, but also utilizing emerging technologies to capturethe energy created from thermal energy sources, vibration sources (e.g.vehicles, machines, buildings, and human motions), and kinetic sources.This captured energy can then be used for various applications. Forexample, capacitors have long been standard equipment in energy storagebut new techniques allow for additional approaches to energy harvesting.

In newer embodiments, the plates of the capacitor may be variable gapcapacitors that are capable of actually generating alternating currentthat can be rectified for power storage. See U.S. Patent Pub. No.20190386584 (“Energy Harvesting Devices and Sensors and Methods ofMaking and Use Thereof”), which is incorporated by reference as if setforth fully herein. In the commonly owned '584 publication, a plate(optionally a graphene membrane) is fixed at one end and will vibrate upand down between two extremes when it is excited by applied energy,ambient energy, vibrations, heat, light and the like. By flexing andoscillating between the two extremes, the strain/stress developed on thesurface of the plate can be used to capture energy.

In one example, vibrations at the atomic scale are omnipresent, even ina mechanically quiet environment. This is due to the material being heldat some temperature above absolute zero, and are called thermalvibrations. It is with respect to these and other considerations thatthe various embodiments described below are presented.

Thermal energy, such as that which induces the vibrations describedabove, also induce electrical responses in numerous other circuits. Thesignals generated by thermal energy, however, must not only be capturedbut also transformed into reliable, consistent power signals if theenergy is to be harvested for use in other applications. A needcurrently exists in the energy sector for circuits, methods, and systemsused to harvest electrical energy produced by thermal systems, even inambient thermal conditions.

BRIEF SUMMARY OF THE DISCLOSURE

In one embodiment, an energy harvesting system includes a DC voltagesource connected to at least one capacitor that generates an AC noisesignal. A selected bandwidth of the AC noise signal transmits throughthe capacitor as a first AC power signal, and respective diodes rectifythe first power signal to charge a positive cycle storage capacitor anda negative cycle storage capacitor with the first AC power signal.

In another embodiment, the AC noise signal is a thermal noise signal andthe at least one capacitor is a plurality of capacitors connected inseries.

In another embodiment, the capacitor is configured with storage capacityof 1 pico-Farad.

In another embodiment, the first AC power signal is rectified through aforward biased diode during a positive cycle of the first AC powersignal to produce an output power signal.

In another embodiment, the first AC power signal is rectified through areverse biased diode during a negative cycle of the first AC powersignal to produce an output power signal.

In another embodiment, the diodes are paired as a sub-unit and thesubunit is connected to a positive cycle metal trace connection and anegative cycle metal trace connection, and the sub-units are repeatedwith respective connections to the positive cycle metal trace connectionand the negative cycle metal trace connection.

In another embodiment, the forward based diode and the reversed biaseddiode are connected to additional diodes in a Cockcroft-Walton full-waverectifier and multiplier circuit.

In another embodiment, a plurality of capacitors in the energyharvesting system are variable gap capacitors generating both the firstAC power signal from the AC noise signal and a second AC power signalfrom a variable gap capacitor discharge cycle.

In another embodiment, the capacitor is fully charged by the DC voltagesource to a stable state.

In another embodiment, the diodes are selected based on the rate ofconductance to match the capacitor as a noise source.

In another embodiment, the AC noise signal comprises conductivity due toconductive carrier defect hopping through the capacitor.

In another embodiment, the DC voltage source provides a voltage thatcorresponds to turn on voltages for the diodes.

Another embodiment of this disclosure is an integrated circuit on achip, and the integrated circuit includes at least one capacitorconnected to the circuit to generate an AC noise signal. A selectedbandwidth of the AC noise signal transmits through the capacitor as afirst AC power signal. Respective rectifiers receive a positive cycle ofthe first AC power signal and a negative cycle of the first AC powersignal. Output terminals connected to the respective rectifiers andconfigured for connection to an off chip circuit. In another embodiment,the AC noise signal within the circuit results from ambient thermalenergy.

In another embodiment, the integrated circuit is configured to connectto an off chip circuit that has a DC voltage source connected to theplurality of capacitors, a positive cycle storage capacitor and negativecycle storage capacitor charged with the first AC power signal.

In another embodiment, the integrated circuit has a first diodeconfigured as a first respective rectifier of the first AC power signalto produce a first output power signal from a positive cycle of thefirst AC power signal.

In another embodiment of the integrated circuit, a second diode isconfigured as a second respective rectifier of the first AC power signalto produce a second output power signal from a negative cycle of thefirst AC power signal.

In another embodiment of an integrated circuit, the integrated circuithas at least one capacitor generating an AC noise signal. A selectedbandwidth of the AC noise signal transmits through the capacitor as afirst AC power signal. Respectively forward biased and reversed biasedtransistors rectify corresponding positive and negative cycles of the ACnoise signal. Output terminals are connected to the transistors andconfigured for connection to an off chip circuit for energy harvestingfrom output signals.

In a method embodiment, the method of assembling an energy harvestingcircuit includes connecting at least one capacitor within the energyharvesting circuit; forming a capacitive region in the energy harvestingcircuit by defining the at least one capacitor with a first capacitorplate having an initial separation distance with respect to a firstsurface of a free-standing membrane, wherein the first surface of thefree-standing membrane defines a second capacitor plate; exposing thefree standing membrane to ambient thermal energy to induce chargeaccumulation in the capacitive region, the ambient thermal energy alsoinducing a thermal AC noise signal; selecting the capacitance of thecapacitor to select a bandwidth of the AC noise signal transmittingthrough the capacitor as a first AC power signal; and rectifying thefirst AC power signal to charge a positive cycle storage capacitor and anegative cycle storage capacitor with the first AC power signal.

In another embodiment of the method, the method includes positioning themembrane relative to the first capacitor plate such that the membrane isunobstructed and free to vibrate in response to ambient thermal energy,wherein vibration of the membrane defines cyclical ripple formationsalong the first surface, and wherein each ripple formation alternatesbetween a peak and a trough relative to the first capacitor plate tochange the initial separation distance in a variable gap capacitor.

In another embodiment of the method, the method includes discharging thecapacitive region across a respective rectifier to direct accumulatedcharges to add a second power signal to the energy harvesting circuits.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale.

FIG. 1A is a schematic illustration of an energy harvesting circuitaccording to one embodiment of this disclosure.

FIG. 1B is a schematic illustration of an off chip circuit that iscompatible with the energy harvesting circuit according to FIG. 1A tostore energy according to embodiments of this disclosure.

FIG. 2 is a schematic illustration of Nyquist noise signal power plottedalongside voltage versus average power of a rectified noise signal fromthe energy harvesting circuit according to FIG. 1A.

FIG. 3A is a schematic illustration of an energy harvesting circuitaccording to another embodiment of this disclosure and utilizing amultiplier circuit to achieve a DC output according to this disclosure.

FIG. 3B is a schematic illustration of an example energy harvestingcircuit establishing variable gap capacitors with a flexible membranesubject to ripples from ambient energy sources.

FIG. 3C is a cross section schematic of one section of the energyharvesting circuit of FIG. 3B.

FIG. 4 is a schematic illustration of a test set up measuring outputpower signals from an AC noise signal applied to a rectifying circuitaccording to FIG. 3 .

FIG. 5 is a plot of inverse capacitance values versus RMS voltage of theDC voltage source shown in FIG. 1A with the inverse capacitance valuesbeing added in accordance with a series of capacitors as shown in FIG.1A.

FIG. 6 is a schematic illustration of a computer environment in whichthe methods and systems of this disclosure may operate.

FIG. 7 is a plot of test results showing noise voltage from a resistorand 10 pF capacitor connected together in parallel. The noise voltage isa maximum when the source resistance is 100 mega-ohms, which matches theload resistance.

FIG. 8 is a graph that shows the gain vs. input voltage for both an18-stage and 24-stage Schottky Cockcroft-Walton circuit according tothis disclosure.

DETAILED DESCRIPTION

Although example embodiments of the disclosed technology are explainedin detail herein, it is to be understood that other embodiments arecontemplated. Accordingly, it is not intended that the disclosedtechnology be limited in its scope to the details of construction andarrangement of components set forth in the following description orillustrated in the drawings. The disclosed technology is capable ofother embodiments and of being practiced or carried out in various ways.

In the following description, references are made to the accompanyingdrawings that form a part hereof and that show, by way of illustration,specific embodiments or examples.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Ranges may beexpressed herein as from “about” or “approximately” one particular valueand/or to “about” or “approximately” another particular value. When sucha range is expressed, other example embodiments include from the oneparticular value and/or to the other particular value.

In describing example embodiments, terminology will be resorted to forthe sake of clarity. It is intended that each term contemplates itsbroadest meaning as understood by those skilled in the art and includesall technical equivalents that operate in a similar manner to accomplisha similar purpose. It is also to be understood that the mention of oneor more steps of a method does not preclude the presence of additionalmethod steps or intervening method steps between those steps expresslyidentified. Steps of a method may be performed in a different order thanthose described herein without departing from the scope of the disclosedtechnology. Similarly, it is also to be understood that the mention ofone or more components in a device or system does not preclude thepresence of additional components or intervening components betweenthose components expressly identified.

This disclosure illustrates hardware and associate methods by whichnoise energy that is present in all circuits can be directed to powerharvesting circuits for use in other applications. A device forharvesting energy from ambient charge fluctuations may be based on thisdisclosure of a recent discovery that output power can be significantlyamplified by the rate of change in conductance with respect to chargeand/or voltage. The noise energy can be a planned signal of previouslyanticipated frequency and amplitude generated from selected hardware. Inone non-limiting embodiment, a single source of noise energy is used tofeed a noise signal to rectifying circuits for power delivery. Thatsingle source may be a series of capacitors as shown in the attachedfigures.

One non-limiting example of the single source of noise energy may beillustrated with regard to the disclosure of previously published,commonly owned U.S. Patent Pub. No. 20190386584 (“Energy HarvestingDevices and Sensors and Methods of Making and Use Thereof”), shown forexample purposes as FIGS. 3B and 3C herein. FIGS. 3A and 3B areschematic illustrations of a silicon-based integrated circuit 400 withpotentially millions of the energy harvesting elements 225. This designonly has one power supply 200 and one storage capacitor 275, but theseare not limiting factors. A first path (denoted with shading and dashes“- - - -”) is when the current is adding charge to the graphenemembrane, while the second path (denoted with circles “^(∘) ^(∘) ^(∘)”is when the current is adding charge to the fixed storage capacitor 275.The silicon has an array of diode pairs 250A-250 n with a respectivemetal contact 225A-225 n in between each pair of diodes. The metalcontacts 225 serve as the above-mentioned energy harvesting elements ofthe system. Above the metal contact 225 is the freestanding graphene 265and it is in constant motion, forming peaks and troughs in response toambient energy, vibrations and the like as described above. Each smallelectrode 225A-225 n will be used to transport charge back to thegraphene and/or a battery or into the storage capacitor 275 as thegraphene membrane oscillates. This is one method for harvesting energyat the nanoscale with millions of graphene ripples each contributingelectrical charge to the capacitor.

For illustration purposes and without limiting this disclosure to anyone configuration, the embodiment of FIGS. 3A and 3B are notable in thatthe contacts 225A-2251 (or up to 225 n with n being any number ofcontacts) serve as the traffic direction point for a variable capacitorto be charged and discharged in accordance with the earlier describedembodiments. The flexible plate, shown as graphene membrane 265 coveringthe essential components, can be used as a first capacitor plate 335 andthe metal contact 225 may be used as the second capacitor plate 235A-235n to form a variable capacitor (i.e., the distance between plateschanges according to membrane ripples having peaks and troughs. Thesekinds of variable capacitors may be used as respective capacitorsrepresented in the sets of capacitors 105A, 105B, 105C of FIG. 1A. Themembrane may cover the entire circuit as shown or at least the metalcontacts 225 to form the variable capacitor. This variable capacitoroperates the same as the embodiments above in regard to the rippling ofthe membrane 265 occurring due to ambient thermal and vibrationalkinetic energy causing the membrane 265, and thus one of the capacitorplates to be displaced and then return (emitting and storing charge incycles). The cycles cause a corresponding change in the charge on themetal contact 225 such that when the capacitive region between the metalplate 225 and the membrane 265 increases in distance between the plates,the charge collected on the metal contact is displaced toward thestorage capacitor for harvesting. When the capacitive region between theplates 235, 335 of the variable capacitor 120 is at its smallest (i.e.,the plates are closest together during a ripple trough), the capacitivecharge is at Cmax with charge collected on the metal contact 235. In theexample shown for the integrated circuit 400, during peak ripple timesin a window region of the graphene membrane 265, positive chargecarriers collected onto the metal contact are directed into the storagecapacitor for current flow in the direction of the upward arrow (i.e.,charging the fixed storage capacitor 275). During trough ripple times ina window region of the graphene membrane 265, positive charge carriersare further collected onto the metal contact with the negative carriersdirected onto the graphene membrane 265 for current flow in thedirection of the downward arrow (i.e., charging the voltage source 200).

FIG. 3C shows a side view of a cross section of the integrated circuitshown in FIG. 3B. A layered integrated circuit 400 includes the abovedescribed voltage source or battery 200, a fixed storage capacitor 275,and a harvesting circuit formed in a substrate such as but not limitedto a silicon wafer 205. The freestanding membrane 265 is formed over thestructure, and in this non-limiting example, the membrane is made ofgraphene. The diodes 250 are formed in the silicon wafer substrate 205.Stand-off supports 210 ensure proper separation and are sources ofthermal as well as kinetic ambient energy. The freestanding graphenemembrane 265 has a first surface 125A and second surface 125B with thefirst surface serving as a capacitor plate 335. The silicon waferincludes a metal contact 225 that is another capacitor plate 235 asdiscussed above. In certain embodiments that do not limit thisdisclosure, the freestanding graphene membrane 265 may be incorporatedinto a grid 258 that defines window regions for pairing with the metalcontacts in forming the variable capacitor disclosed herein.

In another example, preliminary embodiment, an energy harvesting devicehaving a power source for ambient thermal and vibration energyharvesting is disclosed, having an atomic two-dimensional membrane forbuckling at a relatively low frequency. In non-limiting embodiments, theactive component of the membrane can be carbon from graphite that isisolated. In certain embodiments, the source can use freestandinggraphene which has a substantially large velocity component in thevelocity probability distribution. A vibrating membrane may be a sourceof the noise signal but also another source of AC power released duringdischarge cycles of a capacitor fitted with the membrane. See U.S.Patent Pub. No. 20190386584, cited above.

Devices according to embodiments of the disclosed technology can beincorporated into a variety of systems, devices, and methods forextracting energy, including discharge sensors, force and mass sensors,and self-powered devices with longer charge life.

Devices according to embodiments of the disclosed technology are alsocontemplated for use as a mass detection device or flow charge sensor.For example, in certain implementations, an analytical computercomponent operatively connected with a two-dimensional membrane willhave a predetermined sensitivity operable to sense and harnessrelatively low frequency vibrations from the membrane. Accordingly, thetwo-dimensional membrane will be subject to a buckling frequency andwhen a predetermined change is detected based on presence of a massproximate the membrane, an output as to the detection of the mass willbe determined and transmitted, due to the sensitivity of the membrane ofthe device to vibrations caused by forces originating at the mass.

The origin or source of energy collected in the above non-limitingexamples is primarily thermal energy. In some non-limiting embodiments,the technology used to gather this energy will be silicon-basedintegrated circuits that have been custom designed. Once designed, thecircuit can then be built by a commercially available semiconductorfoundry service. This disclosure will also be amenable for amanufacturer to work directly with a multi-project wafer (MPW)third-party service.

One non-limiting design discussed below is shown in FIG. 1A andreferences FIGS. 3B and 3C. As shown in FIGS. 3B and 3C, and describedin detail in co-pending U.S. Patent Pub. No. 20190386584, there is aseries of capacitors connected to two diodes, and this is an energyharvesting circuit. In one non-limiting example, the sets of capacitors105A, 105B, 105C of FIG. 1A may be variable-gap capacitors as shown inFIGS. 3B and 3C, discussed above and below, and as capacitor plates movethey produce an AC voltage. The diodes of FIG. 1A then rectify this ACvoltage signal.

At the top of FIG. 1A are three contact pads labeled D1, C, and D2. Theyallow access to the chip. D1 only connects to the left line of diodes,D2 only connects to the right diodes, and C only connect to the seriesof capacitors. The terms “right,” “left,” “top,” “bottom,” “vertical”and horizontal are used as example orientations with respect to theschematic illustration of FIGS. 1A and 1B and are not limiting of thisdisclosure. One example design, therefore, is made of verticallyrepeated subunits illustrated for example purposes as repetitive groupsof diode pairs and sets of capacitors in series. More explicitly, inFIG. 1A, a first subunit 102A includes a first diode pair 110A, 120A anda first set 105A of capacitors in series; a second subunit 102B includesa second diode pair 110B, 120B and a second set 105B of capacitors inseries; a third subunit 102C includes a third diode pair 110C, 120C anda third set 105C of capacitors in series. In an example embodiment, eachsubunit therefore has two diodes 110A, 120A, 110B, 120B, 110C, 120Cconnected together and aligned to pass current in the same direction. InFIG. 1A, the positive cycle of the circuit current would flow right toleft.

Continuing with FIG. 1A, the output of the left most diodes 110A, 110B,110C are connected together by a common metal trace called the diode 1(D1) trace 141. The D1 trace 141 is also connected to a first contactpad 130 associated with D1 near the top left of the chip in therepresentation of FIG. 1A, which is used for off-chip access. Similarly,the input signal of the right most diodes 120A, 120B, 120C in thenon-limiting figures are connected together by a common metal tracecalled the diode 2 (D2) trace 143. The D2 trace 143 is also connected toa second contact pad 140 labeled D2 near the top right of FIG. 1A andused for off-chip access. In each subunit, a respective middle metaltrace 145A, 145B, 145C connects the two diodes together and has arespective third metal trace 131A, 131B, 131C coming off in the verticaldirection of the figure. This third metal trace 131A, 131B, 131Cconnects to a respective series of capacitors 105A, 105B, 105C at afirst end of the capacitors. At the second end of the series ofcapacitors, a common metal trace exists and is called the capacitor (C)trace 142. The C trace 142 connects all the second ends of thecapacitors together, and connects the capacitors to a contact padlabeled C 135 near the top and used for off-chip access. In an exampleassembly, the pattern of subunits of diodes and capacitors is thenrepeated thousands of times going down and across the chip, similar tothat shown in FIG. 3B. The chip will have a limited number ofconnections for off-chip access. The minimum number of off-chip contactswould be three (D1, D2, and C). As discussed further below, instead ofthe power depending solely on the conductance, this device output showsthat power also depends on the rate of change in conductance. This canboost the output power significantly.

Instead of using diodes above, this disclosure also includes usingactive rectification MOSFETs. This will provide a lower “turn-on”voltage and therefore provide lower losses. When active rectification isused, additional metal traces and metal contact pads will be requiredfor off-chip access. These contacts allow power to be delivered to thechips MOSFET components.

The capacitance of the capacitors used above will be as small aspossible and in non-limiting embodiments, may generally be less than 1pico-Farad (pF). By adding the capacitors in series as shown in FIG. 1A(i.e., using the series of capacitors 105A, 105B, 105C for each of thesingle variable capacitors 225A-225 n of FIG. 3B), the design lowers thecapacitance by the number in the series. In other words, for each of thevariable capacitors 225A-225 n of FIG. 3B, one non-limiting constructionincorporates several variable capacitors 105A, 105B, 105C in a series asshown in FIG. 1A and using the thermal noise of these series ofcapacitances to boost the power output of the circuit. For example, byhaving ten 1 pF capacitors in series the total capacitance of the serieswould then become 0.1 pF. The thermal voltage produced by the capacitorscan be considered the power source (i.e., the noise power sourcediscussed above). Matching this voltage to the diode performance willhelp minimize losses and maximize the output power.

Recent theoretical discovery disclosed herein shows a power boost overthe traditional Nyquist theory, as shown in FIG. 2 . This power boostoccurs when non-linear devices like diodes and the series of capacitorsare used. FIG. 2 illustrates a comparison of an exact theoretical modelpredicting an output power boost from the design of this disclosure,above Nyquist's theory, when non-linear devices like diodes are used.Equation 1 represents the historical Nyquist finding:

<T/(R+R _(E))C>  Eq. 1

The angle backets, < >, denote that the value plotted in FIG. 2 is theaverage value. Inside the brackets, T is for Temperature, and R is for aload resistance (i.e., the device or application connected to thecircuit of FIG. 1A and drawing power). R has a constant value. C is thecapacitance value, such as, but not limited to, a variable capacitanceof a plate-graphene junction as described in U.S. Patent Pub. No.20190386584 and shown in FIG. 3B. R_E is the equivalent resistance oftwo diodes that, in this example embodiment, are in opposition as shownin FIG. 3C. The value of R_E is not constant but depends on the currentflowing in the circuit. After all, current is the time rate of change inthe charge. The Nyquist plot 215 of FIG. 2 is average power output at D2140 for voltages at D2 140 of FIG. 1 .

Equation 2 represents at least one advancement disclosed herein:

<∂/∂_(q)(T/R+R _(E) ∂H/∂q)>  Eq. 2

Here the new term has the variable H in it. H is the total energy of oneplate of one variable capacitor, such as the graphene 265 of FIGS. 3B,3C (i.e., the Hamiltonian value of the system). In the non-limitingexample of FIGS. 3A, 3B, the energy of the graphene membrane depends onthe charge, q. Therefore, with d representing change (delta), dH/dq=q/C.If R_E was constant, then d/dq(dH/dq)=1/C and gives us the Nyquistformula. But, the d/dq term also expresses the rate of change inresistance for the diodes as the charge changes (changing charge iscurrent). The calculation cannot be written in a simple form, so theformula's value is plotted as an exact output 208 to graphically showthe enhancement over the Nyquist formula. The test set-up 405 plottingthese results 410, 412 from a test circuit 418, 422 monitored by acomputer 427 is shown in FIG. 4 . Numerous computerized components maybe incorporated into all embodiments of this disclosure.

The graph of FIG. 5 shows the output noise voltage for variouscapacitors as tested according to this disclosure. The plot 505 showsoutput voltage vs. 1/C. It is notable that the larger the values of 1/C,the larger the output voltage. The smallest capacitance shown at 515 isnot limiting of this disclosure but is 10{circumflex over ( )}-12 Farads(1 pF).

FIGS. 1A and 1B have been described above as showing a firstnon-limiting embodiment. An energy harvesting system as shown in FIG. 1Bincludes an on chip circuit 100 (shown in detail in FIG. 1A) and an offchip circuit 102 (that may be comparable, but not limited to, to thecircuits of FIGS. 3A, 3B for discussion purposes). The off chip circuit102 includes a DC voltage source 150 connected to a plurality ofcapacitors 105A, 105B, 105C in the on chip circuit 100 that areconnected in series, as discussed above, and generate an AC noise signalon lines 131A, 131B, 131C. This connection is shown in FIG. 1B at thecontact pad labeled C 135 connecting the C trace 142 of FIG. 1 as the ACvoltage source. By choosing capacitors of planned specifications, aselected bandwidth of the AC noise signal is transmitted through theseries of capacitors 105A, 105B, 105C as a first AC power signal. Thecapacitors take into account noise response such as measures of noisesignal standard deviation. In one non-limiting theory of operation, theAC noise signal includes, at least, conductivity due to conductivecarrier defect hopping through the capacitors. The first AC noise signal131A, 131B, 131C is directed to respective diodes 110A, 110B, 110C,120A, 120B, 120C rectifying the first power signal to charge a positivecycle storage capacitor 160 and negative cycle storage capacitor 170with the first AC power signal. The series of capacitors reduces anoverall capacitance of the series as a whole due to the additive natureof reciprocal capacitances in the example series. In one non-limitingembodiment the capacitors are configured with a storage capacity of onepicofarad (1 pF).

FIG. 1 takes advantage of an AC noise signal 131A, 131B, 131C that ispresent across the series of capacitors, and in one non-limitingembodiment, the noise signal is thermal noise. The thermal noise can becontrolled, in part at least, by the ambient conditions of a chipbearing the circuit of FIGS. 1A and 1B. For example the circuit of FIG.1A may be exposed to a heated environment to increase the amplitude ofthermal noise. The first AC noise signal 131A, 131B, 131C is a subset offrequencies of the ambient noise signal that transmit through thecapacitors. The first AC noise signal is rectified through a forwardbiased diode 110A, 110B, 110C during a positive cycle of the first ACnoise signal to produce an output power signal. The first AC noisesignal is further rectified through a reverse biased diode 120A, 120B,120C during a negative cycle of the first AC power signal to produce acorresponding output power signal. The diodes may be paired as part of asubunit and the subunit is connected to a positive cycle metal traceconnection 141 and a negative cycle metal trace connection 143. Thesub-units are repeated with respective connections to the positive cyclemetal trace connection and the negative cycle metal trace connection.

In some non-limiting versions of the embodiment shown in FIGS. 1A and 1Bthe plurality of capacitors are fully charged by a DC voltage source(similar to FIG. 3B Ref. 200), positioned either off chip (FIG. 1B) oron chip if necessary, to a stable state. The DC voltage source 200provides a voltage that corresponds to turn on voltages for the diodesor other nonlinear circuit components in use. The diodes are selectedbased on the rate of conductance to match the plurality of capacitors asa noise source.

In another embodiment, the forward based diode and the reversed biaseddiode are connected to additional diodes in a Cockcroft-Walton full-waverectifier and multiplier circuit as shown in FIG. 3A. The AC noisesignal 131A, 131B, 131C shown in FIG. 1A as an output from the series ofcapacitors 105A, 105B, 105C can be connected to a positive terminal 308Aand a negative terminal 308B. The full wave rectifier establishes amultiple of input power in stages having a forward biased diode 310 andreverse biased diode 320, and rectified power signals are directed to aDC output 365.

The circuits of the corresponding figures herein may make use of aplurality of capacitors 305 having variable gap capacitors generatingboth the first AC power signal from the AC noise signal and a second ACpower signal from a variable gap capacitor discharge. The variable gapcapacitor technology is discussed above and U.S. Patent Pub. No.20190386584 (“Energy Harvesting Devices and Sensors and Methods ofMaking and Use Thereof”), which is incorporated by reference as if setforth fully herein, discusses that technology in detail.

As shown in FIG. 1A and FIG. 1B the energy harvesting circuit may beimplemented as an integrated circuit on a chip. FIG. 1A illustrates anon-chip circuit having a plurality of capacitors that are connected inseries and generate the above-described AC noise signal. A selectedbandwidth of the AC noise signal transmits through the series ofcapacitors as a first AC power signal. Respective rectifiers receive apositive cycle of the first AC power signal and a negative cycle of thefirst AC power signal. Output terminals connected to the respectiverectifiers and configured for connection to an off chip circuit. In onenon-limiting embodiment shown in FIG. 1B, the off chip circuit mayinclude companion circuits including but not limited to a DC voltagesource connected to the plurality of capacitors, a positive cyclestorage capacitor and negative cycle storage capacitor charged with thefirst AC power signal. When the off chip circuit is configured as inFIGS. 3B, 3C, the normal operation of discharging the capacitive regionsacross a respective rectifier also directs accumulated charges to add asecond power signal to the energy harvesting circuits. In other words,the rectified thermal noise signal 131A, 131B, 131C of this disclosureis a first power signal and in some embodiments, normal variablecapacitor energy harvesting as shown in FIGS. 3B, 3C are a second powersignal for energy harvesting.

The variable gap capacitor technology discussed above lends itself to anefficient energy harvesting circuit. The steps of that method mayinclude, at least, connecting a series of capacitors within the energyharvesting circuit; for each of the capacitors in the series, forming acapacitive region in the energy harvesting circuit by defining a firstcapacitor plate having an initial separation distance with respect to afirst surface of a free-standing membrane. The first surface of thefree-standing membrane defines a second capacitor plate. Exposing thefree standing membrane to ambient thermal energy induces chargeaccumulation in the capacitive region, and the ambient thermal energyalso inducing a thermal AC noise signal. The method includes selectingthe capacitance of the capacitors to select a bandwidth of the AC noisesignal transmitting through the series of capacitors as a first AC powersignal. In accordance with the rest of this disclosure, the methodincludes rectifying the first AC power signal to charge a positive cyclestorage capacitor and a negative cycle storage capacitor with the firstAC power signal. Implementing the method includes, in non-limitingembodiments, positioning the membrane relative to the first capacitorplate such that the membrane is unobstructed and free to vibrate inresponse to ambient thermal energy. The vibration of the membranedefines cyclical ripple formations along the first surface, and eachripple formation alternates between a peak and a trough relative to thefirst capacitor plate to change the initial separation distance in avariable gap capacitor. Discharging the capacitive region across arespective rectifier directs accumulated charges to add a second powersignal to the energy harvesting circuits.

Experimental Disclosure

As discussed in the above referenced patent publication for energyharvesting, U.S. Patent Pub. No. 20190386584 (“Energy Harvesting Devicesand Sensors and Methods of Making and Use Thereof”), the linear powerformula found from models for the output power is similar to Nyquist'sformula P=kBT/RC. Here C is the average capacitance of the fluctuatinggraphene. Under certain modelling condition, the total movement of thegraphene can be made small, but the formula is still the same. Thismeans that a fixed capacitor should also work and give the same formula,where the fixed capacitance is the average capacitance. Testing hasshown that the output power is enhanced at lower frequencies. Themechanism in the main, but non-limiting, model used herein, is theslower rate at which the graphene inverts its curvature due to a buildupof strain. In one non-limiting theory of operation, the conductionmechanism (barrier crossing rate), is thought to be the origin of all1/f noise.

As it turns out, 1/f noise is present in all electronics, includingfixed capacitors (thought to be due to defect hopping). This means thata fixed capacitor will also give enhanced power at lower frequencies.The voltage fluctuations for output of a variable gap capacitor (Vrms)for graphene experiments are small and around 30 mV. Since one goal isto rectify the signal, it is best to have this voltage be at or abovethe “turn on” diode voltage (200 mV for Schottky). Silicon diodes (turnon is 700 mV) have also been tested to active rectification using MOSFETtechnology. These device require a small amount of power to operate, buttheir turn-on voltage is only 10 mV. Comparing applications in the solarindustry, the ohmic losses when using silicon were much greater than thepower used to drive the MOSFETs. This allows us to take full advantageof the amplifier benefits offered by transistors.

One test example, such as shown in FIG. 4 , was built in the form of afull-wave rectifier 418 with an added times ten multiplier circuit outof passive diodes and capacitors to test this. Recalling that a noisesignal would, in reality, originate from a series of capacitors, butwhen a simulated test input a noise signal 410, 412 having a Vrms of 200mV (mean of zero), the output 422 was 2 V DC as shown forexperimentation on a multimeter 427. Since this worked for Schottky (andsilicon at 700 mV), this same theory of operation will work at 10 mVwith MOSFETs. Voltage being low is not a problem. For fixed capacitors,the voltage is lower than graphene, but fixed capacitors demonstrate inthe lab that when one connects 16 capacitors in series, for example, theoutput voltage rises by a factor of four. The results of this disclosureand associated testing indicates that by designing associated integratedcircuits, users can have them built by known foundry sources. In onenon-limiting embodiment, the circuits can be laid out any way desiredand generally have over 10,000 circuit elements on a 2.5 mm by 2 mmchip. In one example, the smallest capacitance capacitor that oneexample foundry makes is 0.2 pF, which is small enough (plus thefootprint is tiny). This leads to the conclusion that one can design anarray of these capacitors, followed by the active rectificationmultiplier circuit to produce a power generating chip with currenttechnology. This chip would be low risk, low cost, and would help uswork toward the more powerful graphene chip.

In addition as further discovered in the research model, that whencapacitors are arranged with diodes and resistors in a particularcircuit layout, the output power is boosted above the known formula forthe Nyquist comparison.

As shown in FIG. 7 , this disclosure successfully developed a detailedphysical understanding of the Nyquist noise voltage. The noise voltageincreases with decreasing capacitance as originally predicted. Thisdisclosure also illustrates an increase in the noise power by a factorof about ten, when the test circuit adds a specific resistor value inparallel with the series of capacitors 105A, 105B, 105C. The value ofthe resistance must match the resistance of the circuit used to measurethe noise power. The data for this discovery is shown in FIG. 7 . Here,the noise voltage originating from a 10 pF capacitor is shown as afunction of the resistance value of the resistor connected in parallelwith the 10 pF capacitor. When the parallel resistance is 100 mega-ohms,the noise voltage is a maximum. This resistance is the same as themeasurement circuit. With no resistor added in parallel, the noisevoltage drops by a factor of 10. No resistor amounts to adding anextremely large resistance in parallel. The trend line for adding toolarge of a resistance is shown by the squares in FIG. 7 .

As shown in FIG. 8 , this disclosure tested three rectifier-multipliercircuit topologies on a breadboard, and then tested them using a noisepower input source. The topologies are known as differential drive,charge pump, and Schottky Cockcroft-Walton. Unfortunately, thedifferential drive actually divides the signal instead of multiplies.The other two topologies multiply the signal, but the SchottkyCockcroft-Walton provides the best performance. The gain for both an18-stage and a 24-stage Schottky Cockcroft-Walton rectifier-multipliercircuit as a function of the input noise voltage is shown in FIG. 8 .When the input noise voltage has an rms value of 10 mV, the outputvoltage is about five times larger, or 50 mV DC. In the silicon waferchip, the results show the input rms noise voltage to be 100 mV, inwhich case, the output voltage is a very respectable 3.5 volts DC.

FIG. 6 of this disclosure shows that the computerized system describedherein may be used in conjunction with equipment that monitors orassists with energy harvesting. New models/functions can be pushed tovarious servers and cloud based servers if necessary.

Implementations described above and in relation to FIGS. 1 through 6 maybe used with equipment that implements computerized methods that areactivated with an electronic control unit (“ECU”) 600. In particular,the described equipment, including computers used as part of a systemcommunicate with a computer processor configured to process one or morecharacteristics and/or profiles of the electrical signals received. Byway of example and without limiting this disclosure to any particularhardware or software, FIG. 6 illustrates a block diagram of a systemherein according to one implementation.

The ECU 600 may include a computing unit 606, a system clock 608, anoutput module 610 and communication hardware 612. In its most basicform, the computing unit 606 may include a processor 604 and a systemmemory 610. The processor 602 may be a standard programmable processorthat performs arithmetic and logic operations necessary for operation ofthe sensor system 600. The processor 602 may be configured to executeprogram code encoded in tangible, computer-readable media. For example,the processor 602 may execute program code stored in the system memory604, which may be volatile or non-volatile memory. The system memory 604is only one example of tangible, computer-readable media. In one aspect,the computing unit 606 can be considered an integrated device such asfirmware. Other examples of tangible, computer-readable media includefloppy disks, CD-ROMs, DVDs, hard drives, flash memory, or any othermachine-readable storage media, wherein when the program code is loadedinto and executed by a machine, such as the processor 602, the machinebecomes an apparatus for practicing the disclosed subject matter.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the vehicle computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

What is claimed is:
 1. An energy harvesting system, comprising: a DCvoltage source connected to at least one capacitor that generates an ACnoise signal; a selected bandwidth of the AC noise signal transmittingthrough the capacitor as a first AC power signal; and respective diodesrectifying the first power signal to charge a positive cycle storagecapacitor and a negative cycle storage capacitor with the first AC powersignal.
 2. The system of claim 1, wherein the AC noise signal is athermal noise signal and the at least one capacitor is a plurality ofcapacitors connected in series.
 3. The system of claim 1, wherein thecapacitor is configured with storage capacity of 1 pico-Farad.
 4. Thesystem of claim 1, further comprising the first AC power signalrectified through a forward biased diode during a positive cycle of thefirst AC power signal to produce an output power signal.
 5. The systemof claim 4, further comprising the first AC power signal rectifiedthrough a reverse biased diode during a negative cycle of the first ACpower signal to produce an output power signal.
 6. The system of claim5, wherein the diodes are paired as a sub-unit and the subunit isconnected to a positive cycle metal trace connection and a negativecycle metal trace connection, and the sub-units are repeated withrespective connections to the positive cycle metal trace connection andthe negative cycle metal trace connection.
 7. The system of claim 5,wherein the forward based diode and the reversed biased diode areconnected to additional diodes in a Cockcroft-Walton full-wave rectifierand multiplier circuit.
 8. The system of claim 1, wherein the pluralityof capacitors comprises variable gap capacitors generating both thefirst AC power signal from the AC noise signal and a second AC powersignal from a variable gap capacitor discharge cycle.
 9. The system ofclaim 1, wherein the capacitor is fully charged by the DC voltage sourceto a stable state.
 10. The system of claim 1, wherein the diodes areselected based on the rate of conductance to match the capacitor as anoise source.
 11. The system of claim 1, wherein the AC noise signalcomprises conductivity due to conductive carrier defect hopping throughthe capacitor.
 12. The system of claim 1, wherein the DC voltage sourceprovides a voltage that corresponds to turn on voltages for the diodes.13. An integrated circuit on a chip, the circuit comprising: at leastone capacitor connected to the circuit to generate an AC noise signal; aselected bandwidth of the AC noise signal transmitting through thecapacitor as a first AC power signal; respective rectifiers receiving apositive cycle of the first AC power signal and a negative cycle of thefirst AC power signal; output terminals connected to the respectiverectifiers and configured for connection to an off chip circuit.
 14. Theintegrated circuit of claim 13, wherein the AC noise signal results fromambient thermal energy.
 15. The integrated circuit of claim 13,configured to connect to the off chip circuit that comprises a DCvoltage source connected to the plurality of capacitors, a positivecycle storage capacitor and negative cycle storage capacitor chargedwith the first AC power signal.
 16. The integrated circuit of claim 13,further comprising a first diode configured as a first respectiverectifier of the first AC power signal to produce a first output powersignal from a positive cycle of the first AC power signal.
 17. Theintegrated circuit of claim 16, further comprising a second diodeconfigured as a second respective rectifier of the first AC power signalto produce a second output power signal from a negative cycle of thefirst AC power signal.
 18. An integrated circuit, comprising: at leastone capacitor generating an AC noise signal; a selected bandwidth of theAC noise signal transmitting through the capacitor as a first AC powersignal; respectively forward biased and reversed biased transistorsrectifying corresponding positive and negative cycles of the AC noisesignal; output terminals connected to the transistors and configured forconnection to an off chip circuit for energy harvesting from outputsignals.
 19. A method of assembling an energy harvesting circuit,comprising: connecting at least one capacitor within the energyharvesting circuit; forming a capacitive region in the energy harvestingcircuit by defining the at least one capacitor with a first capacitorplate having an initial separation distance with respect to a firstsurface of a free-standing membrane, wherein the first surface of thefree-standing membrane defines a second capacitor plate; exposing thefree standing membrane to ambient thermal energy to induce chargeaccumulation in the capacitive region, the ambient thermal energy alsoinducing a thermal AC noise signal; selecting the capacitance of thecapacitor to select a bandwidth of the AC noise signal transmittingthrough the capacitor as a first AC power signal; and rectifying thefirst AC power signal to charge a positive cycle storage capacitor and anegative cycle storage capacitor with the first AC power signal.
 20. Themethod of claim 19, further comprising, positioning the membranerelative to the first capacitor plate such that the membrane isunobstructed and free to vibrate in response to ambient thermal energy,wherein vibration of the membrane defines cyclical ripple formationsalong the first surface, and wherein each ripple formation alternatesbetween a peak and a trough relative to the first capacitor plate tochange the initial separation distance in a variable gap capacitor. 21.The method of claim 20, further comprising discharging the capacitiveregion across a respective rectifier to direct accumulated charges toadd a second power signal to the energy harvesting circuits.